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fixing issues from #152.
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pigpigyyy committed Oct 21, 2023
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180 changes: 101 additions & 79 deletions doc/docs/doc/README.md
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Expand Up @@ -389,6 +389,80 @@ tb::func! if tb != nil
</pre>
</YueDisplay>

### Chaining Comparisons

Comparisons can be arbitrarily chained:

```moonscript
print 1 < 2 <= 2 < 3 == 3 > 2 >= 1 == 1 < 3 != 5
-- output: true
a = 5
print 1 <= a <= 10
-- output: true
```
<YueDisplay>
<pre>
print 1 < 2 <= 2 < 3 == 3 > 2 >= 1 == 1 < 3 != 5
-- output: true

a = 5
print 1 <= a <= 10
-- output: true
</pre>
</YueDisplay>

Note the evaluation behavior of chained comparisons:

```moonscript
v = (x)->
print x
x
print v(1) < v(2) <= v(3)
--[[
output:
2
1
3
true
]]
print v(1) > v(2) <= v(3)
--[[
output:
2
1
false
]]
```
<YueDisplay>
<pre>
v = (x)->
print x
x

print v(1) < v(2) <= v(3)
--[[
output:
2
1
3
true
]]

print v(1) > v(2) <= v(3)
--[[
output:
2
1
false
]]
</pre>
</YueDisplay>

The middle expression is only evaluated once, rather than twice as it would be if the expression were written as `v(1) < v(2) and v(2) <= v(3)`. However, the order of evaluations in a chained comparison is undefined. It is strongly recommended not to use expressions with side effects (such as printing) in chained comparisons. If side effects are required, the short-circuit `and` operator should be used explicitly.

### Table Appending
The **[] =** operator is used to append values to tables.

Expand Down Expand Up @@ -984,17 +1058,17 @@ Typically when you see a table literal, {1,2,3}, it is on the right hand side of
This is best explained with examples. Here is how you would unpack the first two values from a table:

```moonscript
thing = {1, 2}
thing = [1, 2]
{a, b} = thing
[a, b] = thing
print a, b
```
<YueDisplay>

<pre>
thing = {1, 2}
thing = [1, 2]

{a, b} = thing
[a, b] = thing
print a, b
</pre>
</YueDisplay>
Expand Down Expand Up @@ -1921,6 +1995,19 @@ t = {
</pre>
</YueDisplay>

Lua tables have both an array part and a hash part, but sometimes you want to make a semantic distinction between array and hash usage when writing Lua tables. Then you can write Lua table with **[ ]** instead of **{ }** to represent an array table and writing any key value pair in a list table won't be allowed.

```moonscript
some_values = [ 1, 2, 3, 4 ]
list_with_one_element = [ 1, ]
```
<YueDisplay>
<pre>
some_values = [ 1, 2, 3, 4 ]
list_with_one_element = [ 1, ]
</pre>
</YueDisplay>

## Comprehensions

Comprehensions provide a convenient syntax for constructing a new table by iterating over some existing object and applying an expression to its values. There are two kinds of comprehensions: list comprehensions and table comprehensions. They both produce Lua tables; list comprehensions accumulate values into an array-like table, and table comprehensions let you set both the key and the value on each iteration.
Expand All @@ -1930,12 +2017,12 @@ Comprehensions provide a convenient syntax for constructing a new table by itera
The following creates a copy of the items table but with all the values doubled.

```moonscript
items = { 1, 2, 3, 4 }
items = [ 1, 2, 3, 4 ]
doubled = [item * 2 for i, item in ipairs items]
```
<YueDisplay>
<pre>
items = { 1, 2, 3, 4 }
items = [ 1, 2, 3, 4 ]
doubled = [item * 2 for i, item in ipairs items]
</pre>
</YueDisplay>
Expand Down Expand Up @@ -1969,18 +2056,18 @@ The for and when clauses can be chained as much as desired. The only requirement
Using multiple for clauses is the same as using nested loops:

```moonscript
x_coords = {4, 5, 6, 7}
y_coords = {9, 2, 3}
x_coords = [4, 5, 6, 7]
y_coords = [9, 2, 3]
points = [{x, y} for x in *x_coords \
points = [ [x, y] for x in *x_coords \
for y in *y_coords]
```
<YueDisplay>
<pre>
x_coords = {4, 5, 6, 7}
y_coords = {9, 2, 3}
x_coords = [4, 5, 6, 7]
y_coords = [9, 2, 3]

points = [{x, y} for x in *x_coords \
points = [ [x, y] for x in *x_coords \
for y in *y_coords]
</pre>
</YueDisplay>
Expand Down Expand Up @@ -2035,12 +2122,12 @@ no_color = {k, v for k, v in pairs thing when k != "color"}
The **\*** operator is also supported. Here we create a square root look up table for a few numbers.

```moonscript
numbers = {1, 2, 3, 4}
numbers = [1, 2, 3, 4]
sqrts = {i, math.sqrt i for i in *numbers}
```
<YueDisplay>
<pre>
numbers = {1, 2, 3, 4}
numbers = [1, 2, 3, 4]
sqrts = {i, math.sqrt i for i in *numbers}
</pre>
</YueDisplay>
Expand Down Expand Up @@ -2405,15 +2492,6 @@ You can write range checking code with an `in-expression`.
```moonscript
a = 5
if a in [1, 10]
print "a is in range from 1 to 10"
if a not in [1, 10]
print "a is not in range from 1 to 10"
if a in (0, 11)
print "a is between 0 and 11 with open intervals"
if a in {1, 3, 5, 7}
print "checking equality with discrete values"
Expand All @@ -2424,15 +2502,6 @@ if a in list
<pre>
a = 5

if a in [1, 10]
print "a is in range from 1 to 10"

if a not in [1, 10]
print "a is not in range from 1 to 10"

if a in (0, 11)
print "a is between 0 and 11 with open intervals"

if a in {1, 3, 5, 7}
print "checking equality with discrete values"

Expand Down Expand Up @@ -2649,53 +2718,6 @@ switch item
</pre>
</YueDisplay>

### Range Matching

You can do range matching in a switch when clause using `In` expressions.

```moonscript
value = 5
switch item
-- range checking with closed interval
when in [1, 3]
print "1 <= value <= 3"
-- range checking with open and closed interval
when in (6, 8]
print "6 < value <= 8"
-- not in range checking
when not in [1, 10)
print "not (1 <= value < 10)"
-- checking discrete values
when in {11, 21, 99}
print "value is 11, 21 or 99"
```
<YueDisplay>
<pre>
value = 5

switch item
-- range checking with closed interval
when in [1, 3]
print "1 <= value <= 3"

-- range checking with open and closed interval
when in (6, 8]
print "6 < value <= 8"

-- not in range checking
when not in [1, 10)
print "not (1 <= value < 10)"

-- checking discrete values
when in {11, 21, 99}
print "value is 11, 21 or 99"
</pre>
</YueDisplay>

## Object Oriented Programming

In these examples, the generated Lua code may appear overwhelming. It is best to focus on the meaning of the Yuescript code at first, then look into the Lua code if you wish to know the implementation details.
Expand Down
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