A variant type designed as the unitype for the template language. Any value referenced in a template, returned from within a template, or used in a template context, will be a GVal. m, in most cases, should be a Monad.

Some laws apply here, most notably:

• when isNull is True, then all of asFunction, asText, asNumber, asHtml, asList, asDictItems, and length should produce Nothing
• when isNull is True, then asBoolean should produce False
• when asNumber is not Nothing, then asBoolean should only return False for exactly zero
• Nothing-ness of length should match one or both of asList / asDictItems

Marshal a GVal between carrier monads. This will lose asFunction information, because functions cannot be transferred to other carrier monads, but it will keep all other data structures intact.

Marshal a GVal between carrier monads. Unlike marshalGVal, asFunction information is retained by hoisting them using the provided hoisting functions. For Run monads, which is what GVal is typically used with, the hoistRun function can be used to construct suitable hoisting functions.

Convenience wrapper around asDictItems to represent a GVal as a HashMap.

A function that can be called from within a template execution context.

Match arguments passed to a function at runtime against a list of declared argument names. matchFuncArgs argNames argsPassed returns (matchedArgs, positionalArgs, namedArgs), where matchedArgs is a list of arguments matched against declared names (by name or by position), positionalArgs are the unused positional (unnamed) arguments, and namedArgs are the unused named arguments.

Types that implement conversion to GVal.

Silly helper function, needed to bypass the default Show instance of Scientific in order to make integral Scientifics look like integers.

Turn a Function into a GVal

A key/value pair, used for constructing dictionary GVals using a compact syntax.

Construct a dictionary GVal from a list of pairs. Internally, this uses a hashmap, so element order will not be preserved.

Construct an ordered dictionary GVal from a list of pairs. Internally, this conversion uses both a hashmap (for O(1) lookup) and the original list, so element order is preserved, but there is a bit of a memory overhead.

Construct a pair from a key and a value.

Alias for (~:).

This operator allows constructing heterogenous lists using cons-style syntax, e.g.:

>>> asText $ list ("Found " ~: (6 :: Int) ~: " items" ~: [] :: [GVal IO])
"Found 6 items"

Construct a GVal from a list of GVals. This is equivalent to the toGVal implementation of [GVal m], but typed more narrowly for clarity and disambiguation.

Check if the given GVal is a list-like object

Check if the given GVal is a dictionary-like object

Treat a GVal as a flat list and look up a value by integer index. If the value is not a List, or if the index exceeds the list length, return Nothing.

Helper function; look up a value by an integer index when the index may or may not be available. If no index is given, return Nothing.

Strictly-typed lookup: treat value as a dictionary-like object and look up the value at a given key.

Loosely-typed lookup: try dictionary-style lookup first (treat index as a string, and container as a dictionary), if that doesn't yield anything (either because the index is not string-ish, or because the container doesn't provide dictionary-style access), try index-based lookup.

Like lookupLoose, but fall back to the given default value if the key is not in the dictionary, or if the indexee is not a dictionary-like object.

Treat a GVal as a dictionary and list all the keys, with no particular ordering.

Convert a GVal to a number.

Convert a GVal to an Int. The conversion will fail when the value is not numeric, and also if it is too large to fit in an Int.

Convert a GVal to an Integer The conversion will fail when the value is not an integer

Convert a GVal to an Int, falling back to the given default if the conversion fails.

Convert a GVal to an Int, falling back to zero (0) if the conversion fails.

Loose cast to boolean.

Numeric zero, empty strings, empty lists, empty objects, Null, and boolean False are considered falsy, anything else (including functions) is considered true-ish.

Dynamically cast to a function. This yields Just a Function if the value is a function, Nothing if it's not.