44 lines
1.6 KiB
Markdown
44 lines
1.6 KiB
Markdown
# Lua API documentation
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We the [Lua](http://www.lua.org) script language to customize and
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extend [Lean](http://leanprover.net). This
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[link](http://www.lua.org/docs.html) is a good starting point for
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learning Lua. In this document, we focus on the Lean specific APIs.
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Most of Lean components are exposed in the Lua API.
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**Remark:** the script [md2lua.sh](md2lua.sh) extracts the Lua code
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examples from the `*.md` documentation files in this directory.
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## Hierarchical names
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In Lean, we use _hierarchical names_ for identifying configuration
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options, constants, and kernel objects. A hierarchical name is
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essentially a list of strings and integers.
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The following example demonstrates how to create and manipulate
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hierarchical names using the Lua API.
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```lua
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local x = name("x") -- create a simple hierarchical name
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local y = name("y")
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-- In Lua, 'assert(p)' succeeds if 'p' does not evaluate to false (or nil)
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assert(x == name("x")) -- test if 'x' is equal to 'name("x")'
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assert(x ~= y) -- '~=' is the not equal operator in Lua
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assert(x ~= "x")
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assert(is_name(x)) -- test whether argument is a hierarchical name or not.
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assert(not is_name("x"))
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local x1 = name(x, 1) -- x1 is a name composed of the string "x" and number 1
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assert(tostring(x1) == "x::1")
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assert(x1 ~= name("x::1")) -- x1 is not equal to the string x::1
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assert(x1 == name("x", 1))
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local o = name("lean", "pp", "colors")
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-- The previous construct is syntax sugar for the following expression
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assert(o == name(name(name("lean"), "pp"), "colors"))
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assert(x < y) -- '<' is a total order on hierarchical names
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local h = x:hash() -- retrieve the hash code for 'x'
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assert(h ~= y:hash())
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```
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