Merge pull request #221 from fastfloat/fortran

Fortran support (with fixes)

Author: lemire

README.md

@@ -55,6 +55,34 @@ int main() {
 }
 ```
 
+You can parse delimited numbers:
+```C++
+  const std::string input =   "234532.3426362,7869234.9823,324562.645";
+  double result;
+  auto answer = fast_float::from_chars(input.data(), input.data()+input.size(), result);
+  if(answer.ec != std::errc()) {
+    // check error
+  }
+  // we have result == 234532.3426362.
+  if(answer.ptr[0] != ',') {
+    // unexpected delimiter
+  }
+  answer = fast_float::from_chars(answer.ptr + 1, input.data()+input.size(), result);
+  if(answer.ec != std::errc()) {
+    // check error
+  }
+  // we have result == 7869234.9823.
+  if(answer.ptr[0] != ',') {
+    // unexpected delimiter
+  }
+  answer = fast_float::from_chars(answer.ptr + 1, input.data()+input.size(), result);
+  if(answer.ec != std::errc()) {
+    // check error
+  }
+  // we have result == 324562.645.
+```
+
+
 
 Like the C++17 standard, the `fast_float::from_chars` functions take an optional last argument of
 the type `fast_float::chars_format`. It is a bitset value: we check whether
@@ -115,7 +143,7 @@ int main() {
 }
 ```
 
-## Using commas as decimal separator
+## Advanced options:  using commas as decimal separator, JSON and Fortran
 
 
 The C++ standard stipulate that `from_chars` has to be locale-independent. In
@@ -140,33 +168,72 @@ int main() {
 }
 ```
 
-You can parse delimited numbers:
+You can also parse Fortran-like inputs:
+
 ```C++
-  const std::string input =   "234532.3426362,7869234.9823,324562.645";
-  double result;
-  auto answer = fast_float::from_chars(input.data(), input.data()+input.size(), result);
-  if(answer.ec != std::errc()) {
-    // check error
-  }
-  // we have result == 234532.3426362.
-  if(answer.ptr[0] != ',') {
-    // unexpected delimiter
-  }
-  answer = fast_float::from_chars(answer.ptr + 1, input.data()+input.size(), result);
-  if(answer.ec != std::errc()) {
-    // check error
-  }
-  // we have result == 7869234.9823.
-  if(answer.ptr[0] != ',') {
-    // unexpected delimiter
-  }
-  answer = fast_float::from_chars(answer.ptr + 1, input.data()+input.size(), result);
-  if(answer.ec != std::errc()) {
-    // check error
-  }
-  // we have result == 324562.645.
+#include "fast_float/fast_float.h"
+#include <iostream>
+
+int main() {
+    const std::string input =  "1d+4";
+    double result;
+    fast_float::parse_options options{ fast_float::chars_format::fortran };
+    auto answer = fast_float::from_chars_advanced(input.data(), input.data()+input.size(), result, options);
+    if((answer.ec != std::errc()) || ((result != 10000))) { std::cerr << "parsing failure\n"; return EXIT_FAILURE; }
+    std::cout << "parsed the number " << result << std::endl;
+    return EXIT_SUCCESS;
+}
 ```
 
+You may also enforce the JSON format ([RFC 8259](https://datatracker.ietf.org/doc/html/rfc8259#section-6)):
+
+
+```C++
+#include "fast_float/fast_float.h"
+#include <iostream>
+
+int main() {
+    const std::string input =  "+.1"; // not valid
+    double result;
+    fast_float::parse_options options{ fast_float::chars_format::json };
+    auto answer = fast_float::from_chars_advanced(input.data(), input.data()+input.size(), result, options);
+    if(answer.ec == std::errc()) { std::cerr << "should have failed\n"; return EXIT_FAILURE; }
+    return EXIT_SUCCESS;
+}
+```
+
+By default the JSON format does not allow `inf`:
+
+```C++
+
+#include "fast_float/fast_float.h"
+#include <iostream>
+
+int main() {
+    const std::string input =  "inf"; // not valid in JSON
+    double result;
+    fast_float::parse_options options{ fast_float::chars_format::json };
+    auto answer = fast_float::from_chars_advanced(input.data(), input.data()+input.size(), result, options);
+    if(answer.ec == std::errc()) { std::cerr << "should have failed\n"; return EXIT_FAILURE; }
+}
+```
+
+
+You can allow it with a non-standard `json_or_infnan` variant:
+
+```C++
+#include "fast_float/fast_float.h"
+#include <iostream>
+
+int main() {
+    const std::string input =  "inf"; // not valid in JSON but we allow it with json_or_infnan
+    double result;
+    fast_float::parse_options options{ fast_float::chars_format::json_or_infnan };
+    auto answer = fast_float::from_chars_advanced(input.data(), input.data()+input.size(), result, options);
+    if(answer.ec != std::errc() || (!std::isinf(result))) { std::cerr << "should have parsed infinity\n"; return EXIT_FAILURE; }
+    return EXIT_SUCCESS;
+}
+``````
 
 ## Relation With Other Work
 

include/fast_float/ascii_number.h

@@ -347,9 +347,17 @@ parsed_number_string_t<UC> parse_number_string(UC const *p, UC const * pend, par
     return answer;
   }
   int64_t exp_number = 0;            // explicit exponential part
-  if ((fmt & chars_format::scientific) && (p != pend) && ((UC('e') == *p) || (UC('E') == *p))) {
+  if ( ((fmt & chars_format::scientific) &&
+        (p != pend) &&
+        ((UC('e') == *p) || (UC('E') == *p)))
+       ||
+       ((fmt & FASTFLOAT_FORTRANFMT) &&
+        (p != pend) &&
+        ((UC('+') == *p) || (UC('-') == *p) || (UC('d') == *p) || (UC('D') == *p)))) {
     UC const * location_of_e = p;
-    ++p;
+    if ((UC('e') == *p) || (UC('E') == *p) || (UC('d') == *p) || (UC('D') == *p)) {
+      ++p;
+    }
     bool neg_exp = false;
     if ((p != pend) && (UC('-') == *p)) {
       neg_exp = true;

include/fast_float/float_common.h

@@ -13,14 +13,18 @@
 namespace fast_float {
 
 #define FASTFLOAT_JSONFMT (1 << 5)
+#define FASTFLOAT_FORTRANFMT (1 << 6)
 
 enum chars_format {
   scientific = 1 << 0,
   fixed = 1 << 2,
   hex = 1 << 3,
   no_infnan = 1 << 4,
+  // RFC 8259: https://datatracker.ietf.org/doc/html/rfc8259#section-6
   json = FASTFLOAT_JSONFMT | fixed | scientific | no_infnan,
+  // Extension of RFC 8259 where, e.g., "inf" and "nan" are allowed.
   json_or_infnan = FASTFLOAT_JSONFMT | fixed | scientific,
+  fortran = FASTFLOAT_FORTRANFMT | fixed | scientific,
   general = fixed | scientific
 };
 

tests/CMakeLists.txt

@@ -73,8 +73,7 @@ fast_float_add_cpp_test(powersoffive_hardround)
 fast_float_add_cpp_test(string_test)
 
 fast_float_add_cpp_test(json_fmt)
-
-
+fast_float_add_cpp_test(fortran)
 
 option(FASTFLOAT_EXHAUSTIVE "Exhaustive tests" OFF)
 

tests/fortran.cpp

@@ -0,0 +1,69 @@
+/*
+ * Exercise the Fortran conversion option.
+ */
+#include <cstdlib>
+#include <iostream>
+#include <vector>
+
+#define FASTFLOAT_ALLOWS_LEADING_PLUS
+
+#include "fast_float/fast_float.h"
+
+
+int main_readme() {
+    const std::string input =  "1d+4";
+    double result;
+    fast_float::parse_options options{ fast_float::chars_format::fortran };
+    auto answer = fast_float::from_chars_advanced(input.data(), input.data()+input.size(), result, options);
+    if((answer.ec != std::errc()) || ((result != 10000))) { std::cerr << "parsing failure\n" << result <<"\n"; return EXIT_FAILURE; }
+    std::cout << "parsed the number " << result << std::endl;
+    return EXIT_SUCCESS;
+}
+
+int main ()
+{
+  const std::vector<double> expected{ 10000, 1000, 100,  10, 1,    .1, .01, .001, .0001 };
+  const std::vector<std::string> fmt1{ "1+4", "1+3", "1+2", "1+1", "1+0", "1-1", "1-2",
+    "1-3", "1-4" };
+  const std::vector<std::string> fmt2{ "1d+4", "1d+3", "1d+2", "1d+1", "1d+0", "1d-1",
+    "1d-2", "1d-3", "1d-4" };
+  const std::vector<std::string> fmt3{ "+1+4", "+1+3", "+1+2", "+1+1", "+1+0", "+1-1",
+    "+1-2", "+1-3", "+1-4" };
+  const fast_float::parse_options options{ fast_float::chars_format::fortran };
+
+  for ( auto const& f : fmt1 ) {
+    auto d{ std::distance( &fmt1[0], &f ) };
+    double result;
+    auto answer{ fast_float::from_chars_advanced( f.data(), f.data()+f.size(), result,
+                                                  options ) };
+    if ( answer.ec != std::errc() || result != expected[std::size_t(d)] ) {
+      std::cerr << "parsing failure on " << f << std::endl;
+      return EXIT_FAILURE;
+    }
+  }
+
+  for ( auto const& f : fmt2 ) {
+    auto d{ std::distance( &fmt2[0], &f ) };
+    double result;
+    auto answer{ fast_float::from_chars_advanced( f.data(), f.data()+f.size(), result,
+                                                  options ) };
+    if ( answer.ec != std::errc() || result != expected[std::size_t(d)] ) {
+      std::cerr << "parsing failure on " << f << std::endl;
+      return EXIT_FAILURE;
+    }
+  }
+
+  for ( auto const& f : fmt3 ) {
+    auto d{ std::distance( &fmt3[0], &f ) };
+    double result;
+    auto answer{ fast_float::from_chars_advanced( f.data(), f.data()+f.size(), result,
+                                                  options ) };
+    if ( answer.ec != std::errc() || result != expected[std::size_t(d)] ) {
+      std::cerr << "parsing failure on " << f << std::endl;
+      return EXIT_FAILURE;
+    }
+  }
+  if(main_readme() != EXIT_SUCCESS) { return EXIT_FAILURE; }
+
+  return EXIT_SUCCESS;
+}

tests/json_fmt.cpp

@@ -8,6 +8,34 @@
 
 #include "fast_float/fast_float.h"
 
+int main_readme() {
+    const std::string input =  "+.1"; // not valid
+    double result;
+    fast_float::parse_options options{ fast_float::chars_format::json };
+    auto answer = fast_float::from_chars_advanced(input.data(), input.data()+input.size(), result, options);
+    if(answer.ec == std::errc()) { std::cerr << "should have failed\n"; return EXIT_FAILURE; }
+    return EXIT_SUCCESS;
+}
+
+
+int main_readme2() {
+    const std::string input =  "inf"; // not valid in JSON
+    double result;
+    fast_float::parse_options options{ fast_float::chars_format::json };
+    auto answer = fast_float::from_chars_advanced(input.data(), input.data()+input.size(), result, options);
+    if(answer.ec == std::errc()) { std::cerr << "should have failed\n"; return EXIT_FAILURE; }
+    return EXIT_SUCCESS;
+}
+
+int main_readme3() {
+    const std::string input =  "inf"; // not valid in JSON but we allow it with json_or_infnan
+    double result;
+    fast_float::parse_options options{ fast_float::chars_format::json_or_infnan };
+    auto answer = fast_float::from_chars_advanced(input.data(), input.data()+input.size(), result, options);
+    if(answer.ec != std::errc() || (!std::isinf(result))) { std::cerr << "should have parsed infinity\n"; return EXIT_FAILURE; }
+    return EXIT_SUCCESS;
+}
+
 int main()
 {
   const std::vector<double> expected{ -0.2, 0.02, 0.002, 1., 0., std::numeric_limits<double>::infinity() };
@@ -36,5 +64,8 @@ int main()
     }
   }
 
+  if(main_readme() != EXIT_SUCCESS) { return EXIT_FAILURE; }
+  if(main_readme2() != EXIT_SUCCESS) { return EXIT_FAILURE; }
+
   return EXIT_SUCCESS;
 }