<s>
Source	O
is	O
a	O
family	O
of	O
sublanguages	O
of	O
JavaScript	B-Language
,	O
developed	O
for	O
the	O
textbook	O
Structure	B-Language
and	I-Language
Interpretation	I-Language
of	I-Language
Computer	I-Language
Programs	I-Language
,	I-Language
JavaScript	I-Language
Edition	I-Language
(	O
SICP	B-Language
JS	I-Language
)	O
.	O
</s>
<s>
The	O
JavaScript	B-Language
sublanguages	O
Source	O
§1	O
,	O
Source	O
§2	O
,	O
Source	O
§3	O
and	O
Source	O
§4	O
are	O
designed	O
to	O
be	O
just	O
expressive	O
enough	O
to	O
support	O
all	O
examples	O
of	O
the	O
respective	O
chapter	O
of	O
the	O
textbook	O
.	O
</s>
<s>
During	O
the	O
development	O
of	O
SICP	B-Language
JS	I-Language
,	O
starting	O
in	O
2008	O
,	O
it	O
became	O
clear	O
that	O
purpose-designed	O
sublanguages	O
of	O
JavaScript	B-Language
would	O
contribute	O
to	O
the	O
learning	O
experience	O
.	O
</s>
<s>
Initially	O
called	O
"	O
JediScript	O
"	O
and	O
inspired	O
by	O
the	O
book	O
"	O
JavaScript	B-Language
:	O
The	O
Good	O
Parts	O
"	O
by	O
Douglas	O
Crockford	O
,	O
the	O
Source	O
sublanguages	O
follow	O
the	O
chapters	O
of	O
SICP	B-Language
JS	I-Language
;	O
each	O
language	O
Source	O
§x	O
is	O
a	O
sublanguage	O
of	O
the	O
next	O
language	O
Source	O
§( x+1	O
)	O
.	O
</s>
<s>
Following	O
the	O
minimalistic	O
approach	O
of	O
SICP	B-Language
JS	I-Language
,	O
implementations	O
of	O
Source	O
are	O
expected	O
to	O
remove	O
any	O
JavaScript	B-Language
language	I-Language
features	O
that	O
are	O
not	O
included	O
in	O
the	O
language	O
specification	O
.	O
</s>
<s>
Source	O
§1	O
is	O
a	O
very	O
small	O
purely	O
functional	B-Language
sublanguage	O
of	O
JavaScript	B-Language
,	O
designed	O
for	O
Chapter	O
1	O
of	O
SICP	B-Language
JS	I-Language
.	O
</s>
<s>
Chapter	O
5	O
of	O
SICP	B-Language
JS	I-Language
does	O
not	O
require	O
language	O
support	O
beyond	O
Source	O
§4	O
.	O
</s>
<s>
All	O
Source	O
languages	O
are	O
properly	B-Language
tail	I-Language
recursive	I-Language
,	O
as	O
required	O
by	O
Chapter	O
1	O
of	O
SICP	B-Language
and	O
as	O
specified	O
by	O
ECMAScript	B-Language
2015	O
.	O
</s>
<s>
Since	O
the	O
Safari	B-Application
browser	I-Application
is	O
ECMAScript-2015-compliant	O
,	O
including	O
proper	B-Language
tail	I-Language
calls	I-Language
,	O
it	O
can	O
serve	O
as	O
an	O
implementation	O
of	O
all	O
Source	O
languages	O
,	O
provided	O
that	O
the	O
SICP	B-Language
package	O
is	O
loaded	O
.	O
</s>
<s>
The	O
Source	O
Academy	O
is	O
a	O
web-based	B-Application
programming	O
environment	O
that	O
implements	O
all	O
Source	O
languages	O
,	O
regardless	O
of	O
browser	O
support	O
for	O
proper	B-Language
tail	I-Language
calls	I-Language
,	O
and	O
features	O
various	O
tools	O
for	O
the	O
readers	O
of	O
SICP	B-Language
JS	I-Language
.	O
</s>
