goblin

goblin is an embeddable scripting engine written in Go.

Notes

To regenerate parser.go, you need to have goyacc installed:

go get -u golang.org/x/tools/cmd/goyacc/...

Syntax

Comments

# Single line, commented to end of line
// Single line, commented to end of line
/*
 * Multi-line comment.
 */

Variable declaration and assignment

Note that while the descriptions below mention specific types, variables can generally be converted transparently from one type to another, possibly with some lossiness.

a = 1                    // Numeric 64-bit integer value
b = 0xaf                 // Numeric 64-bit integer value
c = 1.2                  // Numeric 64-bit float value
d = 1.2e7                // Numeric 64-bit float value
e = true                 // Boolean value
f = "hello"              // String value
g = [ 1, 2, 3 ]          // Slice containing numeric 64-bit integer values
h = [ 1.2, 3.4 ]         // Slice containing numeric 64-bit float values
i = [ 1, 1.2, "hello" ]  // Slice containing a mixture of values
j = { "foo": "bar" }     // Map with key "foo"
k = { "a": 1, "b": 2.1 } // Map with keys "a" and "b"
l = nil                  // The nil value

Variable types

typeOf(1)             // int64
typeOf(1.2)           // float64
typeOf(true)          // bool
typeOf([1,2])         // []interface{}
typeOf({"foo": "bar") // map[string]interface{}
typeOf("foo")         // string
typeOf(nil)           // <nil>

Operators

=      // Assignment
==     // Equal
!      // Not
!=     // Not equal
>      // Greater than
>=     // Greater than or equal to
<      // Less than
<=     // Less than or equal to
+      // Add
+=     // Add and assign
-      // Subtract
-=     // Subtract and assign
*      // Multiply
*=     // Multiply and assign
/      // Divide
/=     // Divide and assign
**     // Power
%      // Remainder
%=     // Remainder and assign
|      // Bitwise OR
||     // Logical OR
&      // Bitwise AND
&&     // Logical AND
>>     // Shift right
<<     // Shift left
^      // Bitwise XOR
?      // Ternary operator, as in a == b ? c : d

Loops

for i = 0; i < 10; i++ {
    // C-style for loop from 0-9
}

for i in [1,3,5] {
    // Iterate through a slice
}

for i in range(0,9) {
    // Loop from 0-9
}

for i < 5 {
    // Loop until i >= 5
}

for {
    // Loop forever or until break/return
}

Switch

switch x {
    case 1:
        // Do something on x == 1
    case 2:
        // Do something on x == 2
    case bar():
        // Do something if x == bar()
    default:
        // Do something if no other case was hit
}

If

if x == 1 {
    // Do something on x == 1
} else if x == 2 {
    // Do something on x == 2
} else if x == 3 {
    // Do something on x == 3
} else {
    // Do something if none of the previous comparisons were true
}

Access a slice

a[2:4]  // Return a new slice with the elements at index 2 and 3 of the original slice
a[:4]   // Return a new slice with the elements at indexes 0-3 of the original slice
a[2:]   // Return a new slice with the elements at index 2 and later of the original slice
a[:]    // Return a new slice with the full contents of the original
a[2]    // Return the element at index 2

Define a function

func a() {
    // Do something
}

func b(c) {
    // Do something... has an arg (c) that can be used
}

func d() {
    return 12   // Returns the value 12
}

Built-ins

len(x)           // Returns the length of the slice, map or string
keys(x)          // Returns the keys of a map
range(limit)     // Returns a slice of int64 starting at 0 and going through limit - 1
range(min, max)  // Returns a slice of int64 starting at min and going through max
sort(a, func(i, j) { return a[i] < a[j] }) // Sorts an array. The second parameter is a function that should test for the element at index i being less than the element at index j.
sleep("1s")      // Sleep for a duration, such as "100ms" for 100 milliseconds, "1s" for one second, "1m" for one minute, etc. Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", and "h".
toString(x)      // Converts the value to a string
toInt(x)         // Converts the value to an int64
toFloat(x)       // Converts the value to a float64
toBool(x)        // Converts the value to a bool
toChar(x)        // Converts the value to a single-character string
toRune(x)        // Converts the value to a rune
toByteSlice(x)   // Converts the value to a []byte
toRuneSlice(x)   // Converts the value to a []rune
toBoolSlice(x)   // Converts the value to a []bool
toIntSlice(x)    // Converts the value to a []int64
toFloatSlice(x)  // Converts the value to a []float64
toStringSlice(x) // Converts the value to a []string
typeOf(x)        // Returns the name of the type x
defined(x)       // Returns true if the variable has been defined
print(x...)      // Same as Go's fmt.Print
println(x...)    // Same as Go's fmt.Println
printf(x...)     // Same as Go's fmt.Printf

richardwilkes / goblin