Merge pull request #4188 from Parashurama/improve_float_parsing

fixes some issues with underscores in float literals. add more tests.

lib/system/sysstr.nim

@@ -328,7 +328,7 @@ proc nimParseBiggestFloat(s: string, number: var BiggestFloat,
     fraction: uint64
     frac_exponent= 0
     exp_sign = 1
-    first_digit = 0
+    first_digit = -1
     has_sign = false
 
   # Sign?
@@ -359,6 +359,7 @@ proc nimParseBiggestFloat(s: string, number: var BiggestFloat,
   # Skip leading zero
   while s[i] == '0':
     inc(i)
+    while s[i] == '_': inc(i)
 
   if s[i] in {'0'..'9'}:
       first_digit = (s[i].ord - '0'.ord)
@@ -366,7 +367,7 @@ proc nimParseBiggestFloat(s: string, number: var BiggestFloat,
   while s[i] in {'0'..'9'}:
     inc(kdigits)
     integer = integer * 10'u64 + (s[i].ord - '0'.ord).uint64
-    inc(i);
+    inc(i)
     while s[i] == '_': inc(i)
 
   # Fractional part?
@@ -374,11 +375,12 @@ proc nimParseBiggestFloat(s: string, number: var BiggestFloat,
     inc(i)
     # if no integer part, Skip leading zeros
     if kdigits <= 0:
-      while s[i] in {'_','0'}:
-        inc(i)
+      while s[i] == '0':
         inc(frac_exponent)
+        inc(i)
+        while s[i] == '_': inc(i)
 
-    if s[i] in {'0'..'9'}:
+    if first_digit == -1 and s[i] in {'0'..'9'}:
       first_digit = (s[i].ord - '0'.ord)
     # get fractional part
     while s[i] in {'0'..'9'}:

tests/float/tfloat6.nim

@@ -0,0 +1,21 @@
+discard """
+  file: "tfloat6.nim"
+  output: '''1e-06 : 1e-06
+1e-06 : 1e-06
+0.001 : 0.001
+1e-06 : 1e-06
+1e-06 : 1e-06
+10.000001 : 10.000001
+100.000001 : 100.000001'''
+"""
+
+import strutils
+
+echo "0.00_0001".parseFloat(), " : ", 1E-6
+echo "0.00__00_01".parseFloat(), " : ", 1E-6
+echo "0.0_01".parseFloat(), " : ", 0.001
+echo "0.00_000_1".parseFloat(), " : ", 1E-6
+echo "0.00000_1".parseFloat(), " : ", 1E-6
+
+echo "1_0.00_0001".parseFloat(), " : ", 10.000001
+echo "1__00.00_0001".parseFloat(), " : ", 1_00.000001

tests/float/tfloat7.nim

@@ -0,0 +1,26 @@
+discard """
+  file: "tfloat6.nim"
+  output: '''passed.
+passed.
+passed.
+passed.
+passed.
+passed.
+passed.'''
+"""
+
+import strutils
+template expect_fail(x: expr) =
+  try:
+    discard x
+    echo("expected to fail!")
+  except ValueError:
+    echo("passed.")
+
+expect_fail("1_0._00_0001".parseFloat())
+expect_fail("_1_0_00.0001".parseFloat())
+expect_fail("10.00.01".parseFloat())
+expect_fail("10.00E_01".parseFloat())
+expect_fail("10.00E_01".parseFloat())
+expect_fail("10.00E".parseFloat())
+expect_fail("10.00A".parseFloat())