Soft scope vs. Hard scope¶

Soft scope (Rule 1)¶

If a binding exists in the global scope, assign to that

In [1]:

s1_global = 0
println(s1_global)
for i=1:1
    println(s1_global)
    s1_global = 1
    println(s1_global)
end
println(s1_global)

If no binding exists, make a new local binding

In [2]:

try
    println(s1_local)
catch
    println("not defined")
end
for i=1:1
    try
        println(s1_local)
    catch
        println("not defined")
    end
    s1_local = 1
    try
        println(s1_local)
    catch
        println("not defined")
    end
end
try
    println(s1_local)
catch
    println("not defined")
end

not defined
not defined
1
not defined

Soft scope (Rule 2)¶

local assignment local x=1 makes a new local binding

In [3]:

s2 = 0
println(s2)
for i=1:1
    try
        println(s2)
    catch
        println("not defined")
    end
    local s2 = 1
    println(s2)
end
println(s2)

0
not defined
1
0

Soft scope (Rule 3)¶

Global assignment global x=1 makes a new global binding

In [4]:

try
    println(s3)
catch
    println("not defined")
end
for i=1:1
    try
        println(s3)
    catch
        println("not defined")
    end
    global s3 = 1
    try
        println(s3)
    catch
        println("not defined")
    end
end
try
    println(s3)
catch
    println("not defined")
end

not defined
not defined
1
1

Hard scope (Rule 1)¶

normal assignment x = 1 make a new local binding

In [5]:

h1 = 0
println(h1)
function f()
    try
        println(h1)
    catch
        println("not defined")
    end
    h1 = 1
    println(h1)
end
f()
println(h1)

0
not defined
1
0

Hard scope (Rule 2)¶

local assignment local x=1 makes a new local binding (equivalent to above)

In [6]:

h2 = 0
println(h2)
function f()
    try
        println(h2)
    catch
        println("not defined")
    end
    local h2 = 1
    println(h2)
end
f()
println(h2)

0
not defined
1
0

Hard scope (Rule 3)¶

global assignment global x=1 makes a new global binding

In [7]:

try
    println(h3)
catch
    println("not defined")
end
function f()
    try
        println(h3)
    catch
        println("not defined")
    end
    global h3 = 1
    println(h3)
end
f()
println(h3)

not defined
not defined
1
1

Conclusion¶

Soft scope and hard scope varies only at the treatment of normal assignment. Soft scope always tries to find a global binding first instead of creating a new local variable as hard scope do.