Make builtin math the default implementation

Remove our `math` function that wraps `bc`. Our math builtin is now good
enough that it can be the default implementation.

Another step in resolving #3157.

share/functions/math.fish

@@ -1,51 +0,0 @@
-function math --description "Perform math calculations in bc"
-    if not set -q argv[2]
-        # Make sure an invocation like `math "-1 + 1"` doesn't treat the string as an option.
-        set argv -- $argv
-    end
-
-    set -l options 'h/help' 's/scale=!_validate_int --min=0' '#-val'
-    argparse -n math --stop-nonopt --min-args=1 $options -- $argv
-    or return
-
-    if set -q _flag_help
-        __fish_print_help math
-        return 0
-    end
-
-    set -l scale 0 # default is integer arithmetic
-    set -q _flag_scale
-    and set scale $_flag_scale
-
-    if set -q _flag_val
-        # The expression began with a negative number. Put it back in the expression.
-        # The correct thing is for the person calling us to insert a `--` separator before the
-        # expression to stop parsing flags. But we'll work around that missing token here.
-        set argv -$_flag_val $argv
-    end
-
-    # Set BC_LINE_LENGTH to a ridiculously high number so it only uses one line for most results.
-    # We can't use 0 since some systems (including macOS) use an ancient bc that doesn't support it.
-    # We also can't count on this being recognized since some BSD systems don't recognize this env
-    # var at all and limit the line length to 70.
-    set -lx BC_LINE_LENGTH 500
-    set -l out (echo "scale=$scale; $argv" | bc)
-    if set -q out[2]
-        set out (string join '' (string replace \\ '' $out))
-    end
-    switch "$out"
-        case ''
-            # No output indicates an error occurred.
-            return 3
-
-        case 0
-            # For historical reasons a zero result translates to a failure status.
-            echo 0
-            return 1
-
-        case '*'
-            # For historical reasons a non-zero result translates to a success status.
-            echo $out
-            return 0
-    end
-end

tests/math.in

@@ -6,7 +6,7 @@ math '10 % 6'
 math -s0 '10 % 6'
 math '23 % 7'
 math --scale=6 '5 / 3 * 0.3'
-math "1 + 1233242342353453463458972349873489273984873289472914712894791824712941"
+math "7^2"
 math -1 + 1
 math '-2 * -2'
 math 5 \* -2

tests/math.out

@@ -1,12 +1,12 @@
 1
 1
 1
-1.666
+1.667
 4
 4
 2
-.499999
+0.500000
-1233242342353453463458972349873489273984873289472914712894791824712942
+49
 0
 4
 -10