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Add signum interpolation function
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This function returns -1 for negative numbers, 0 for 0 and 1 for positive numbers.

Useful when you need to set a value for the first resource and a different value for the rest of the resources.

Example: `${element(split(",", var.r53_failover_policy), signum(count.index))}`
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jfromaniello committed Jan 27, 2016
1 parent d78e897 commit d615c48
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20 changes: 20 additions & 0 deletions config/interpolate_funcs.go
Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,7 @@ func Funcs() map[string]ast.Function {
"length": interpolationFuncLength(),
"lower": interpolationFuncLower(),
"replace": interpolationFuncReplace(),
"signum": interpolationFuncSignum(),
"split": interpolationFuncSplit(),
"sha1": interpolationFuncSha1(),
"sha256": interpolationFuncSha256(),
Expand Down Expand Up @@ -403,6 +404,25 @@ func interpolationFuncLength() ast.Function {
}
}

func interpolationFuncSignum() ast.Function {
return ast.Function{
ArgTypes: []ast.Type{ast.TypeInt},
ReturnType: ast.TypeInt,
Variadic: false,
Callback: func(args []interface{}) (interface{}, error) {
num := args[0].(int)
switch {
case num < 0:
return -1, nil
case num > 0:
return +1, nil
default:
return 0, nil
}
},
}
}

// interpolationFuncSplit implements the "split" function that allows
// strings to split into multi-variable values
func interpolationFuncSplit() ast.Function {
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36 changes: 36 additions & 0 deletions config/interpolate_funcs_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -543,6 +543,42 @@ func TestInterpolateFuncLength(t *testing.T) {
})
}

func TestInterpolateFuncSignum(t *testing.T) {
testFunction(t, testFunctionConfig{
Cases: []testFunctionCase{
{
`${signum()}`,
nil,
true,
},

{
`${signum("")}`,
nil,
true,
},

{
`${signum(0)}`,
"0",
false,
},

{
`${signum(15)}`,
"1",
false,
},

{
`${signum(-29)}`,
"-1",
false,
},
},
})
}

func TestInterpolateFuncSplit(t *testing.T) {
testFunction(t, testFunctionConfig{
Cases: []testFunctionCase{
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5 changes: 5 additions & 0 deletions website/source/docs/configuration/interpolation.html.md
Original file line number Diff line number Diff line change
Expand Up @@ -168,6 +168,11 @@ The supported built-in functions are:
`n` is the index or name of the subcapture. If using a regular expression,
the syntax conforms to the [re2 regular expression syntax](https://code.google.com/p/re2/wiki/Syntax).

* `signum(int)` - Returns -1 for negative numbers, 0 for 0 and 1 for positive numbers.
This function is useful when you need to set a value for the first resource and
a different value for the rest of the resources.
Example: `element(split(",", var.r53_failover_policy), signum(count.index))`

* `split(delim, string)` - Splits the string previously created by `join`
back into a list. This is useful for pushing lists through module
outputs since they currently only support string values. Depending on the
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