### possible bug -fx dealing with signed numbers

Posted:

**2020-02-23T15:30:28-07:00**-fx used to be able to handle signed variables. But lately it fails when the variable's sign and the sign in the function are the same, e.g. a--b or a++b.

This change occurred between IM 6.9.10.83 and 6.9.10.84 (correspondingly between IM 6.9.10.84 and IM 7.0.9.14) and persists to the current versions 6.9.10.95 and 7.0.10.25.

Running on Mac OSX Sierra.

This change occurred between IM 6.9.10.83 and 6.9.10.84 (correspondingly between IM 6.9.10.84 and IM 7.0.9.14) and persists to the current versions 6.9.10.95 and 7.0.10.25.

**Double Minus Sign fails**Code: Select all

```
xmax=492
xmin=-1
im691083 convert xc: -format "%[fx:abs($xmax-$xmin)]" info:
493
im691084 convert xc: -format "%[fx:abs($xmax-$xmin)]" info:
0 <--- WRONG
```

**Minus and Plus Sign works fine:**Code: Select all

```
xmax=492
xmin=+1
im691083 convert xc: -format "%[fx:abs($xmax-$xmin)]" info:
491
im691084 convert xc: -format "%[fx:abs($xmax-$xmin)]" info:
491
```

**Double Plus Sign fails**Code: Select all

```
xmax=492
xmin=+1
im691083 convert xc: -format "%[fx:abs($xmax+$xmin)]" info:
493
im691084 convert xc: -format "%[fx:abs($xmax+$xmin)]" info:
0 <--- WRONG
```